Please refer to FIG. 1, which shows how a driver's visual field is going to change with respect to different driving speeds. As modern transportation means, such as cars, is becoming a necessity in our daily life, it is a common knowledge that the faster a driver is driving a car, the narrow the visual field of the driver will have. As shown in FIG. 1, the visual field range 11 of a driver is about 210 degrees when the vehicle is still, but the range 12 will reduce to about 100 degrees when the vehicle is moving at 40 kilometers per hour; and the visual field range 13 will even reduce to about 65 degrees when it is traveling at 70 kilometers per hour, and moreover the visual field range 14 will even reduce to about 40 degrees when it is traveling at 100 kilometers per hour. Please refer to FIG. 2, which shows how the blind spot area of a driver driving a vehicle is going to change with respect to different driving speeds. It is known that a driver's blind spot area is defined as the portion of the ambient environment in the vicinity of the vehicle in which an object will not normally be observed by the use of the interior and exterior mirrors of the vehicle. As shown in FIG. 2, although the vehicle is attached with interior and exterior rearview mirrors for enabling the driver to see objects in a rear area 16, there are still two blind spot areas 15 formed at the two sides of the vehicle. In addition, it is noted that the faster the vehicle is traveling, the larger the blind spot areas 15 will be.
Please refer to FIG. 3, which is a schematic diagram showing a blind spot area formed at the left-rear side of a vehicle. In FIG. 3, the driver of the vehicle 17 is able to see another vehicle 18 overtaking from the left side thereof from its rearview mirrors as a portion of the vehicle 18 is located inside the visible rear area 19. However, as the overtaking progresses, the whole vehicle is going to enter the blind spot area 20 and become invisible to the driver that might be dangerous if the driver should decide to change to the left lane at the same time.
Please refer to FIG. 4, which shows a vehicle traveling in the visual field of a driver is shielded by another vehicle also traveling in the visual field and thus is hidden. In FIG. 4, the visual field of a driver driving the vehicle 17 is obstructed by another vehicle 21 overtaking from the left side thereof, by which the front left visual field of the vehicle 17 is reduced to a very small area 19 as that enclosed in the dotted line while creating a new blind spot area 20. Therefore, another vehicle 22 traveling in a direction perpendicular to and toward the vehicle 17, which was originally capable of being seen by the driver if there is no such vehicle 21 overtaking the same, will now be traveling in the blind spot area 20 of the vehicle 17 and become invisible to the driver. Thereby, the driver of the vehicle 17 tends to keep driving straight ahead without any aware of the vehicle 22 is approaching from the left so that it is ease to cause traffic accident. Since most drivers will not be aware of the blind spots 20 created by another overtaking vehicle, as those shown in FIG. 3 and FIG. 4, he/she might make some driving decisions with fetal consequences, such as taking a lane change at the wrong time and speed. Therefore, it is in need of a method and apparatus capable of not only tracking any vehicle traveling in the blind spot areas in an effective manner, but also predicting the moving direction and speed of a hidden object when the object originally moving in the visual field of a user is shielded and hidden behind an obstacle while issuing an alarm to warn the user and the same time establishing a recommendation for preventing from colliding with the hidden object.